After user equipment (User Equipment, UE for short) is powered on or when it is roaming, the primary task is to select a public land mobile network (Public Land Mobile Network, PLMN for short) and successfully register with the PLMN, and the UE can obtain normal communications services such as a voice service and a data service only in this way.
In the prior art, after UE is powered on, it first attempts to register with a public land mobile network that the UE successfully registered with (Registered PLMN, RPLMN for short) last time. If the registration fails, the UE performs full-band network searching. The UE searches for all networks according to frequency bands and radio access technologies (Radio Access Technologies, RAT for short) that are supported by the UE, and generates a list of available networks, where each element in the list includes a PLMN and a RAT of an available network. To facilitate faster registration of the UE with an available network, the UE needs to select a PLMN from the foregoing list of the found available networks according to a particular rule. For example, it is stipulated in the 3rd Generation Partnership Project (3rd Generation Partnership Project, 3GPP for short) specifications that UE selects a PLMN according to the following sequence: RPLMN→home public land mobile network (Home PLMN, HPLMN for short)→user controlled public land mobile network (User PLMN, UPLMN for short)→operator controlled public land mobile network (Operator PLMN, OPLMN for short)→other available PLMNs (OTHER Available PLMN).
Duration of network searching performed by the UE mainly depends on factors such as a frequency band and a RAT that are supported by the UE, a quantity of coverage cells in an area in which the UE is located, and software and hardware restrictions of the UE. With commercialization of the Long Term Evolution (Long Term Evolution, LTE for short) technology, the UE can support more RATs. When the UE is roaming, the UE needs to look over all standards and frequency bands that are supported by the UE and generate a list of available networks before selecting a PLMN and attempting to register with the selected PLMN, which results in an excessively long time of network searching.
Duration of PLMN selection performed by the UE mainly depends on an order of the foregoing found available networks in the list. In a scenario in which the UE is roaming, if there is a large quantity of operators in a roaming area of the UE, the list of the found available networks is long, for example, there are many small operators in Hong Kong, America, and some European countries, and the number of elements in the list of available networks may reach dozens. In addition, a PLMN selection process is a trial-and-error process; for each selected PLMN and RAT, a registration attempt process of the UE involves multiple rounds of network-wide signaling message interaction; in addition, when one registration attempt fails, the UE needs to continue to attempt to register with the same PLMN and RAT until a preset stop condition is satisfied, for example, a quantity of failed attempts reaches a preset quantity-of-failed-attempts threshold, leading to an excessively long time of PLMN selection.
In the prior art, when UE initially accesses a network in a roaming area, it takes a relatively long time for the UE to successfully register with a network in the roaming area, and user experience is affected due to an excessively long waiting time.